"I have never done any lobbying," Gingrich said, adding that he only offered "advice as an historian."

For some context, a full-time professor of history made an average of $63,119 per year around 2006. Newt racked up $300,000, or about 4.75 times as much.

But to get at a larger point, lobbying watchdogs say Gingrich's justification shows just how weak lobbying disclosures are and how easy it is to avoid registering.

"It doesn't matter if you're a historian, CEO or pastry chef. If you're advising a group and representing their interests before policymakers, you're lobbying on their behalf -- plain and simple," the Sunlight Foundation's Gabriela Schneider told TPM in an email.

Public Citizen's Craig Holman said this was the first time he'd heard the "ambiguous term 'strategic consultant' replaced with an academic term 'historian,'" but that regardless of the terminology, Gingrich "was hired as a lobbyist for his rolodex built while being a public servant."

Gingrich, Holman told TPM in an email, "represents the worst of revolving door abuse. Gingrich cashed in on his status as a former public official, taking in $300,000 in salary from Freddie Mac to promote the lender's business model one year as a 'strategic consultant' rather than a registered lobbyist in order to avoid disclosure, and then switched sides when the winds of political opportunity shifted."

Holman continued: "This clearly shows that those who swing through the revolving door to promote the business interests of whoever can afford their price tag rarely do so on principle, but merely for self-profit and opportunity."

"Newt Gingrich claiming that he was a 'historian' for housing is a clear example of the inherent weakness of our current definition of lobbyist," Public Citizen's Lisa Gilbert told TPM. "When the requirements for registering are so loose as to enable a former Speaker to claim he was only a $300,000 paid advice giver for Fannie and Freddie, it's time to tighten up the system."

One way to close those loopholes, says Sunlight's Schneider, is to pass reform legislation.

"The current lobbying rules are antiquated and full of loopholes, including allowing these kinds of influentials to lobby without registering as lobbyists," Schneider said. "That's something the Lobbying Disclosure Enhancement Act, introduced by Rep. Quigley a few months ago, would fix."